Conditioning rolls with helical ribs or bars extending in a continuous spiral from one end of the roll to the other have a tendency to load up crop materials along one side of the conditioned crop discharge flow from the rolls. Consequently, the resulting windrows or swaths may be less uniform than desired, with heavier accumulations along one side than the other. This can have an adverse effect upon drying times and hay quality. Moreover, in many harvesters the cutting swath is wider than the centrally disposed inlet opening to the conditioning rolls such that outboard severed materials must be gathered centrally by augers or other means before they can enter the inlet. This increases the likelihood that the discharge flow will have heavier accumulations of materials along its sides than in the middle, in contrast to the desired goal of having the flow as uniform as possible across its entire width.
The present invention provides a novel method and apparatus for obtaining improved crop conditioning. In its broadest aspects it involves the discovery that significantly more uniform distribution can be obtained when the rib pattern is herringbone-shaped, rather than a continuous spiral, and the rolls are constructed from a hard, non-compressible material, such as steel. The herringbone pattern naturally tends to draw the outer materials toward the center of the rolls when the pattern is properly oriented with respect to the direction of roll rotation, and the hard, metal nature of the ribs makes their centering action even more aggressive than would otherwise be the case. This is especially beneficial in harvesters using rotary cutters as the means for severing the standing crop from the ground as these machines tend to run faster and present higher quantities of materials to the rolls in less time than sickle-type machines, presenting an even greater challenge to uniform distribution within the windrow or swath.
In another aspect the present invention contemplates passing the severed materials through dual sets of conditioning rolls wherein both front and rear pairs of the rolls are constructed from metal and have herringbone rib patterns, providing an extra level of conditioning coupled with speed and uniformity that has particular utility for rotary cutoff machines. For sickle-type machines, it may be appropriate to use metal, herringbone rolls at the front and compressive-surface herringbone rolls at the rear.